Combination protractor and scale



April 28, 1931. c, MOORE 1,803,200

COMBINATION PROTRACTOR AND SCALE Filed Dec. 12, 1927 Inventor Attorney F'feo Cush/h Moore 1 k u I Ila- 5 Patented Apr. 28, 1931 FRED oUsHInG MOORE, oF sroKANE, WASHINGTON- COMBINATION rn-oraacron am) SCALE Application. filed December 12 1927. Serial No. 239,319.

My present invention relates to an improved combination protractor and scale which is designed for use as a geometrical instrument that is adapted for various purposes, but particularly designed forjuse in plotting a survey. The instrument comprises the usual type of protractor having a semi-circular limb, and Combined with-this limb is a scale of straightedge ruler. A

1 number of straight edge rulers are used in a set, and these rulers are interchangeable for employment in connection with the semi-circular limb of the protractor. The protractor of course has the usual degree graduations, and the plurality of rulers have vari ous scales of graduations thereon'bymeans of which diflerent combinations may be made between the semi-circular limb and selected rulers. The semi-circular limb is provided with a central portion that permits facile use of the instrument when working from the center point of the protractor, and this central portion may be open, orv providedwith a transparent web. The ends of the semi- 2 circular limb are provided with means that co-act with complementary-means on a selected ruler by-which the latter is fixedin position between the'ends of the semi-circular limb, and of course means are provided for attaching and detaching the interchange able rulers or straight edges; 7

The instrument consists in certain novel combinations and arrangements of parts as will hereinafter be more fully pointed out and claimed. In the accompanying drawings I have illustrated one complete example (and a slight modification) of the physical embodiment of my invention wherein the parts are combined and arrangedaccording to the best mode I have thus far devised for the practical application of the principles of my invention. I

Figure 1 is a plan view of the instrument with a transparent central portion upon which the center point is located.

Figure 2 is an edge view at line 22 of Figure 1 showing the base or straight edge of the protractor.

Figure 3 is a sectional view at line 33 50 of Figure 1.

end of a ruler.

Figure 7 is a detail sectional view at line 77 Figure 1.

Figure 8 is a detail sectional view at line 8-8 of Figure 5. g

Figure 9" is a plan view of a slightly modified central portion of the instrument with the transparent center of Figure 1 omitted.

In carrying out the conception and principles of my invention I employ the well known semi-circular limb 1 of the-protractor which is provided with a-lscale of 180 degrees, and this semi-circular limb is fashioned with abase bar 2 beyond which the two end heads 3, 3, of the circular limb project. These heads 3 are tangential with the curvature of the semi-circular protractor and the outer edges 4 of these heads form straight edges orfaces that are adapted to contact with and be alined withv the blade of a T-square, when theprotractor is being positioned'rtor use. From the base bar"2 a'pair ofangularly disposed bars 5, 5 project, andthese two bars,

together with a portion of the bar 2, form; a I triangular frame in which is inset a trans-' parentplatefi, of glass, celluloid, orother suitable material. The center point C 'for the protractor is indicated bya suitable mark on the transparent insert or panel in Figure 1, and the instrument may be used to work out problems with this point as a center. In

"the modified form indicated in Figure 9 the transparent panel is omitted from the triangular frame, and the center point C ,is lo.- 99 cated on the portion 2 of the base bar 2.1

A radius bar 7 is fashioned integral with thetwo angular bars 5, andthis bar, together with the angular bars, forms a strengthening frame for the semi-circular protractor. The radius bar 7 may be provided with a hole 8 by means of'which the protractor may be hung up on a nail or hook when desired, and the undersideiof thisbar is notched as at 9 to aee-Qmmod'ate th fin a l o a n terchangeable straight edge rulers 10, one of which is shown in the drawings. It'will be understood that a suitable number of these straight edge rulers form the set, and the different rulers of the set have variousgraduations thereonor scales indicated along the V beveled edges of the rulers-. The straight edge ruler is designed to be attached tothe protractor between its spaced heads 3,3, and for this purpose the rulers are provided at their opposite ends with longitudinally extending grooves as 11, and these grooves are counter sunk or counterbored at their'inner ends to form enlarged sockets 12 that may have tapered walls as indicated in the drawings, or the walls may be straight. 1

At the inner sides of the spaced ends or heads 8, are fashioned tenons 13 that project inwardly from the inner faces of these heads, and these tenons are fashioned complementary to the grooves 11 while the tenons terminate in heads 14 that are complementa ry to the sockets l2 and provided with screw holes. The tenons are designed to fit loosely V in the grooves and the heads, which are preferably tapered, are designed also to fit loosely inthe sockets thereby permitting a close adjustment of the parts as they are clamped together for alinement, as indicated in Figure 4. By means of thumb screws 15 passed through screw holes in the part 10 and extending into the screw holes of the heads 1a, and the heads 16 of the screws,the latter may be turned to clamp the straight edge ruler'to the tenonsi The screw holes in'the ruler and in the heads may be in the form of slots or elongated holes to permit drawing together of the adjusted ruler withrelation to the may accurately and closely be secured because of the relatively loose fit between the grooves of the ruler and the tenons of the protractor as well as between the countersunk sockets and their complementary heads, after which the thumb screws are turned to clamp the parts in adjusted position.

Having thus fully described my invention, what I claim as new and desire to secure by Letters Patent is j 1." The combination in a protractor having a base bar and a semi-circular limb terminating in a, pair of spaced heads projecting beyond the base bar and having alined straight edges on their ends, of a straight edge ruler fitted between said heads, co-ac-ting means onithe heads and ruler for engagement in locating the ruler, and clamp means mounted in the co-acting means for fastening the ruler to the heads. i

2.. The-combination with a semi-circular limb having tangential end-heads and alined straight edges on the ends of the heads, of an interchangeable straight edge ruler having grooved ends terminating in countersunk sockets a pairof tenons on the inner sides of said heads adapted to fit said grooves, tapered heads on said tenons adapted to fit said sockets, respectively, 'andclamp screws passing through said taperedheads' for locking the straight edge ruler to the end-heads.

3..;The combination in a protractor having a base bar and a'semi circular limb, a straight edge -ruler and means for securing said ruler to the base bar of the protractor, of an open frame rigid with the limb and base bar, a

ics

' tenons of the protractor. -A screw 15 is used 7 i at each end of the straight edge ruler, and

these screws provide means whereby therulers may be changed with facility and dispatch,- and whereby the rulers may be rigidly clamped in fixed relation to the circular limb of the protractor.

' In Figure 5 the innerbeveled edge of the ruler is shown resting upon the outer edge of the base bar 20f the limb of the protractor,

and this arrangement may be made in order to depress the outer beveled edge of the ruler :so that it will lie flat on t-he supporting surface, and flush with the straight edges or faces 4 of the heads 3. The instrument as thus constructed is adapted for various uses, and may v c 

